During packaging of bulk materials, it is often necessary, to remove at least partly the air which is entrapped between the material particles to thus achieve a sufficient filling of the packing container, especially if earlier for producing a better flow capability of the bulk material air was purposefully introduced into said bulk material. A certain amount of air evacuation can be achieved by leaving the container, for example a bag, open for some minutes after having been filled. When the bulk material settles, the air which exists between the particles is partially removed and escapes upwardly. This method has the disadvantage that the station time within a filling plant must either be held very long or that sufficient space must be provided for the containers which are in the stage after filling, however, prior to closing. Furthermore, devices for the slow further transport of these not as yet closed containers are needed.
To speed up air evacuation, one has also already applied the abovementioned method in which suction probes having an air-permeable surface are introduced into the bulk material (British Pat. No. 965 321, French Pat. No. 1,327,946). The bulk material is thereby already in a packing container, namely a bag. It is true that with this method the air evacuating time can be reduced to a few seconds, however, the packing container must be chosen so large that the measured bulk material portion finds room therein also in the not as yet evacuated condition. After the air evacuation process, the container is then in most cases slightly too large. This means a greater use of packing material than would be necessary in order to pack the air-evacuated portion.
The basic purpose of the invention is to provide a method which permits a designing of the packing container only to the size which is needed for packaging the air-evacuated bulk material portion. Furthermore the invention includes an apparatus for carrying out the method.
The inventive method of the abovementioned type is characterized by a portion of bulk material being filled into a fill pipe during each filling operation, by the gas being evacuated during the stay of the bulk material in the fill pipe and by the portion being thereafter ejected from the fill pipe and being filled into a packing container, preferably a tubelike bag.
Since in the case of the inventive method the air evacuation (or possibly also the evacuation of a different gas) is done prior to the bulk material portion being filled into the packing container, the volume of the portion is during filling into the packing container already as small as it can be after the air evacuation. It is therefore sufficient to provide a packing container which can receive the air-evacuated portion. Thus the size of the container is not chosen, as this is the case in the known method, with consideration of the volume prior to the air evacuation. From this results a substantial saving in packing material.
The further development of the method wherein the container is sealed shut after the evacuation process achieves a further reduction of the air content. This is not supposed to cover primarily air, which is between the particles of the bulk material, but air, which for example is at the upper end of the packing container or possibly in cavities which are created during the pulling out of suction probes. A desired shape of the package and a yet better compactness is achieved with the further development by pressing or compressing the container.
The apparatus embodying the invention has the advantage compared with known devices that operating mechanisms for the suction probes are not needed which brings about a substantial reduction in cost.
A conical construction of the fill pipe has the advantage that the bulk material can be ejected particularly easily from the fill pipe. One must consider that some bulk materials, in particular powdery bulk materials, are compacted to a compact block due to air evacuation so that ejection from the fill pipe is equivalent to a mold release operation.
Fill pipe shapes with an approximately rectangular cross section approximately equal to the cross section of the packing container are particularly advantageous because the bulk material takes on the shape of the packing container already in the fill pipe.
The embodiment having an outer pipe which surrounds the fill pipe is particularly well suited if an additional evacuation after a filling of the bulk material into the packing container is to take place.
An operating mechanism for the fill pipe which is movable in a direction parallel to its axis eases ejection of the bulk material because with the aid of such a mechanism the bulk material is so to speak beaten out of the fill pipe, namely it tears loose from the fill pipe due to its motion energy (momentum) when said fill pipe is suddenly stoppd by a stop.
The inventive apparatus can be constructed as a pure filling device wherein prefabricated packing containers can be supplied in any manner. The packing containers can thereby be both fixed containers, as for example cans, and also flexible containers, thus sacks or bags. According to a further development of the invention, however, the apparatus is combined with a flexible tube bagging machine wherein the fill pipe is at the same time the fill pipe of the flexible tube bagging machine and the lower end of which can be closed off by compressing the casing-material tube by means of cross seal jaws of the flexible tube bagging machine. In this version, in one single aggregate both the manufacture of the packing container, namely the tubelike bag, is effected and also air evacuation and filling of the bulk material into the packing container. In the combination of the apparatus with a flexible tube bagging machine, the already mentioned outer pipe is surrounded by a shaping shoulder for shaping a casing-material tube from a casing-material sheet.
The flat design of the probes has the advantage that only relatively small cavities remain in the bulk material when the bulk material is pulled off from the suction probes. In spite of this, however, one obtains the desired large contact surface between bulk material and the probes. Tapering of the probe eases again ejection of the bulk material from the fill pipe, thus it has a similar function as the already mentioned tapering of the fill pipe.
Through the probe arrangement, the cross section of a rectangularly shaped fill pipe is particularly well engaged and thus an effective air evacuation is achieved in a short time.
The sintered construction of the suction probe has the advantage that the suction openings are small. Such probes are therefore particularly suited for powdery bulk material.
The arrangement embodying the invention has the advantage that after the evacuation of air, a protective gas can be introduced. However, one will introduce only a limited amount of protective gas so that the achieved volume reduction is not again reversed. It is also possible, if necessary, to flow protective gas through the entire bulk material so that the volume can be enlarged and subsequently the protective gas is again evacuated. Thus one is assured that the remaining residual gas is not air containing oxygen, but for example nitrogen. The connection to a pressure air source permits a cleaning of the suction probes after one suction operation. The pressure air is only introduced when the probes are exposed, namely the bulk material has been ejected from the fill pipe.
The pressing mechanism permits a further shaping and compacting of the container content and serves to eliminate cavities in the bulk material.
The further development of the invention permits a mounting of a wrapping packing so to speak in a continuous-flow method, that is a closed packing container is placed automatically into a wrapped container so that an inbetween stacking is not needed.